Adjustable counterbalance crank



March 7, 1956 J. F. EATON 2,739,493

ADJUSTABLE COUNTERBALANCE CRANK Filed June 22, 1951 2 Sheets-Sheet l 30 7 $7 IZWJ' v A- Z2 41 I lg 4 jy- 2. 19 4 ,5 1; l;

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fiva BY r A ATTOR March 27, 1956 J. F. EATON ADJUSTABLE COUNTERBALANCE CRANK 2 Sheets-Sheet 2 Filed June 22, 1951 INVENTQR ain; FEaZan.

ATTOR Y ADJUSTABLE COUNTERBALANCE CRANK John F. Eaton, Tulsa, Okla, assignor to Bethlehem Supply Company, a corporation of Delaware Application June 22, 1951, Serial No. 232,980

14 Claims. (Cl. 74-591) My invention relates in general to improvements in counterbalance cranks for power shafts, and more particularly to an improvement in adjustable counterbalancing means for cranks for oil well drilling and pumping equipment.

In my co-pending application, Serial No. 78,023, filed February 24, 1949, now Patent No. 2,575,075, issued No vember 13, 1951, I have disclosed an adjustable rotary counterbalance crank assembly wherein heavy oppositely disposed weights provided with rollers and pinions are movable on rail-hangers through the engagement of the piuions with gear tooth racks on said arm.

It is an object of my present invention to provide an adjustable counterbalance crank assembly in which only the front crank face and pads on the inner surface of the front counterweight need to be machined.

Another object is a crank assembly characterized by three-point contact between the crank arm and the sliding weights.

A further object is an adjustable counterbalance assembly which is equipped with readily attachable and detachable auxiliary weights.

Still other and further objects, purposes and advantages of my invention will appear hereinafter in the specification and attached two sheets of drawings, and in the appended claims.

in the drawings:

Fig. l is a front elevation of a counterbalance crank unit incorporating the preferred form of my invention, with the upper front counterweight removed and certain other portions shown in section;

Fig. 2 is a bottom plan view of the unit;

Fig. 3 is an elevation of the left end of the unit, shown partly in section;

Fig. 4 is a vertical section taken along the line 4-4 of Fig. 1;

Fig. 5 is an elevation of the right end of the units; and

Fig. 6 is a detail section showing the three point contact mounting of the lower counterweights in the slideway.

Referring now to the drawings, and more particularly to Fig. l, the numeral 1 designates the crank arm, preferably a gray iron casting with a conventional finished and keyed crank shaft hole 2 and a plurality of finished, keyed and tapered wrist pin holes 3, four of the latter being shown, to permit attachment of the wrist pin bearing (not shown) at various distances from the rotating power shaft or crank shaft (also not shown), in accordance with the desired length of pumping stroke. The rear face of the crank arm is provided with a longitudinal central recess 4 adjacent the wrist pin holes 3 so as to allow space for securing the Wrist pin to the crank arm in conventional manner without interfering with the rotation of the crank shaft. Raised bosses 5 and 6 surround the wrist pin holes 3 on both sides of the crank arm. I

Although it will be understood that the drive shaft may be operatively secured in the crank shaft hole 2 by any suitable means, such as a conventional solid hub (not shown) pressed onto the shaft, I prefer to employ a split 2,739,4fl3 Patented Mar. 2?, 1956 hub 7 as shown in Fig. 1 extending to the outer end of the crank arm 1 and adapted to be clamped onto the power shaft by means of hex nut 8 and jam nut 9 on clamp bolt 19 extending vertically through cored bolt holes 11 in said split hub.

Terminal shoulders 12 and 13 are provided to serve as weight stops at each end of the crank arm 1. Extending iongitudinally intermediate said shoulders 12 and 13 are integrally cast vertical top and bottom edge flanges 1d and 15, each flange having a plurality of serrations 16 designed to function as gear teeth, and on the front face of the crank arm 1 between said flanges and the holes for crank shaft and wrist pin are parallel upper and lower longitudinal continuous grooves 17 and 18 constituting slideways for the counterweight assemblies.

The upper and lower counterweight assemblies are identical, being of cast iron and preferably segmental in shape as shown, with each such assembly comprising a front counterweight 19 and a rear counterweight 20, bolted together by means of a fulcrum clamp bolt 21 and two flange clamp bolts 22 secured by nuts 23 and washers 24. For maximum counterbalance effect, auxiliary filler weights 25 fitting into corresponding large recesses 26 in the inner face of the front and rear weights of each counterweight assembly and retained in place by bolts 27 and nuts 28 and having plural recesses 29 engaging support lugs 30 may optionally be provided as shown in Fig. 4. The inner face of each front weight 19 is also provided with two horizontally spaced pairs of small raised integral flange-contacting bosses or pads 31, the pads of each pair being vertically separated, one such pair being located beneath each of the bolts 22, and with a longitudinally extending bottom tongue or shoe 32 which projects horizontally into one of the grooves 17 or 18 of the crank arm 1. Each rear weight 20 has only two inner contact bosses or pads 33, each of which is located approximately midway vertically between the pads 31 of the corresponding pair of pads 31 of the front weight 19 so as to provide three points of clamping contact. Near their outer edges the front and back weights of each assembly are connected together as aforesaid by the fulcrum clamp bolt 21, which passes through a ball-and-socket connection formed by the hemispherical projection 34 on the inner surface of one weight and a corresponding but slightly shallower hemispherical indentation 35 in the other weight, thereby providing a hinge effect which permits the maximum clamping action to be exerted by the pads upon the contacted flange.

Since the two pads 31 of each front weight 19 and the front crank ann face where it is in contact with said pads 31 are machined to exact alignment, each complete weight assembly consisting of one front weight and one rear weight is brought square with and into the plane of rotation of the crank arm 1 when the clamping bolts 22 are tightened and the contacting pads 31 and 33 are pressed against the adjacent flange. The single rear pad 33 serves only to produce the clamping effect in conjunction with the pads 31 on the front Weight, and has no elfect on alignment.

With the crank arm 1 in horizontal position and the flange clamping bolts 22 loosened, each weight assembly is separately movable to the desired position on said crank arm 1 by means of a crank wrench (not shown) engaging a square end 36 of the pinion 37, secured by cotter pins 38, and inserted in bearing bushings 39 in holes 40 in the front and rear weights, and which pinion is provided with suitable teeth 41 engaging the teeth 16 on the crank arm. An index boss 42 on each front weight in cooperation with evenly spaced adjacent legend nuerals 43 on the crank arm 1 serves to mark various adjustment positions of each weight assembly.

Previous types of cranks with adjustable weights have beeuquite expensive to machine, since it has been necessary to face both sides of the edges of the cast iron crank. In my invention, the crank shaft hole 2 and wrist pin holes 3 must still be machined (bored), in common with all cranks, but the only other machined surfaces are. the pads 31 of the front weight and the front face of the crank arm where it comes into contact therewith. The rear weight pads 33 and the rear face of the crank arm do not require machining. Thus, when the crank arm casting is set up and positioned in the boring mill for boring the said crank shaft hole 2 and wrist pin holes 3, after the boring step a face-mill is simply substituted for the boring tool and the front edges of the crank arm are machined at the same set-up arrangement on the same machine, thereby yielding an evident saving in machine set-up time.

It will be understood, of course, that such terms as top and bottom and upper and lower as used hereinabove and in the claims are employed in a relative sense and refer to the positions of the parts as shown in the drawings, more particularly in Fig. 1, since in operationthe positions of the parts will obviously be reversed on each half-revolution of the power shaft.

Although I have described my invention hereinabove in considerable detail, I do not wish to be limited narrowly to the exact and particular structure disclosed, but I may use such substitutes, modifications or equivalents thereof as are embraced within the scope of the invention or pointed out in the appended claims.

I claim:

I. In a counterbalancing device for power shafts, a crank arm adapted to be mounted on a shaft, a flange extending longitudinally of said arm and having a pair of opposed faces substantially parallel to the plane of rotation of the crank arm, and depending weight elements including one member having a pair of clamping projections engaging one face of the flange near its inner and outer edges respectively and another member having a single clamping projection engaging the opposite face of the flange at a point intermediate the points of engagement of said pair of projections.

2. In a counterbalancing device for power shafts, a crank arm adapted to be mounted on a shaft and having a longitudinally extending recess, a flange on said crank arm having a pair of opposed faces substantially parallel to the plane of rotation of the crank arm, a weight element provided with a tongue fitting slidably into said recess, said weight element also being provided with a pair of projections engaging one face of the flange near its inner and outer edges respectively, a separate element having a single projection engaging the opposite face of the flange at a point intermediate the points of engagement of said pair of projections, and means for clamping the flange between said projections.

3. In a counterbalancing device for power shafts, a

crank arm adapted to be mounted on a shaft, a flange extending longitudinally of said arm and having a face parallel to the plane of rotation of the crank arm, a pair of opposed members embracing said flange, a pair of bosses on one member engageable with the aforementioned-face of the crank arm flange near its inner and outer edges respectively, a boss on the other member located at a point intermediate the points of engagement of said pair of bosses and engageable with the opposite face of the crank arm flange, and means for clamping said bosses tightly against the respective faces of thecrank arm flange.

4. In a counterbalancing device for power shafts the combination of a radial crank arm adapted to be mounted onv a shaft, toothed racks integral with the up.- per. and lower edges of the crank arm, parallel longitudinal' grooves forming slideways in one side of the crank arm adjacent the toothed racks, multi-part weight ele ments having supporting shoes slidable within said grooves, crank operable. pinions on said weight elements in meshed engagement with. the toothed racks, andmeans.

5. In a counterbalancing device for power shafts, the

combination as claimed in claim 4, wherein the parts of each weight element comprise a pair of upright weights connected by a hinge member at their outer edge, and clamped against the edges of the crank arm by a plurality of clamp bolts.

6. In a counterbalancing device for power shafts, the combination of a radial crank arm, adapted to be mounted on a shaft, vertical longitudinally extending serrated top and bottom edge flanges cast integral with the crank arm, a pair of longitudinal parallel, grooves forming slideways on the front face of the crank arm, upper and lower counterweight assemblies carrying pinion means engaging the serrated flanges, each such counterweight assembly comprising a front weight and a rear weight, the inner face of each front weight having a plurality of pairs of vertically spaced integral flange-contacting pads and a longitudinally extending continuous tongue pro jecting inwardly into one of the slideways, the inner face ofeach rear weight having individual flange-contacting pads located approximately vertically midway-between thepads of each opposite pair of pads, and means for clamping the pads tightly against their respective flanges and thereby creating a triangular pressure pattern at each of the clamping points.

7. In a counterbalancing device for power shafts, the combination as claimed in claim 6, with ball-and-socket' hinge means connecting the outer edges of the weights of each counterweight assembly.

8. In a counterbalancing device for power shafts, the combination as claimed in claim 6, with a hemispherical indentation near the outer edge of one of the weights of each counterweight assembly, an interfitting hemispherical protuberance on the'companion weight of said assembly, and a bolt through said indentation and protuberance adapted to allow a limited range'of hinging movement of the weights relative to each other.

9. In a counterbalancing device, the combination of a crank arm having longitudinal edge flanges, a pair of longitudinal grooves forming slideways' on the front face of thecrank arm, upper and lower counterweight assemblies adjustably movable along the edge flanges,eachsuch assembly comprising a from weight and a rear weight, each front weight having an inwardly projecting portion movable in one of the slideways and pairs of vertically spaced pads contacting anedge flange, each rear weight having pads contacting the opposite side of said flange approximately midway between the front weight pads, and means for clamping the pads of the counterweight assemblies tightly against the edge flanges.

10. In a counterbalancing device, the combination of a crank arm mounted on a shaft and having a longitudinally extending surface rotatable in a vertical plane, a flange spaced from the crank arm parallel therewith and adapted to rotate in said plane, an offset portion connecting said arm and said flange, rack teeth on theouter edge of'said flange, a counterweight, slidable means associated with thc counterweight having a second flange disposed underneath the rack teeth in the space formed by the above surface and the first-mentioned flange and the offset portion, a pinion mounted in said counterweight and engaging said rack teeth, and means for releasably clamping the counterweight to the crank arm.

11. A counterbalance device as claimed in claim 9, in combination'with ball-and-socket hinge means connecting the outer'edges of'the weights of each counterweight assembly.

12-. A counterbalance device as claimed in claim 9, in combination with a rounded recess adjacent the outer edge of one of the weights of each counterweightassernbly, an interfitting raised portion on the companion weight of said assembly, and a member. connecting said recess and raised. portion and adapted to allow a limited hinging movementofthe weights.

13. In a counterbalancing device, a crank arm having longitudinal edge flanges, a pair of longitudinal recesses on one face of the crank arm, weight elements adjustably movable along the edge flanges, each such element including a pair of opposed detachable members, one of said members having an inwardly projecting portion movable in one recess and pairs of vertically spaced pads contacting an edge flange, a second member having pads contacting the opposite side of said flange approximately midway between the pads of the first member, and means for securing the pads of both members tightly against said edge flange.

14. In a countcrbalancing device for power shafts, a crank arm adapted to be mounted on a shaft and having a longitudinally extending recess, a flange on said crank arm having a pair of opposed faces substantially parallel to the plane of rotation of the crank arm, a weight provided with a tongue fitting slidably into said recess, said weight extending outwardly from said crank arm and in the plane thereof, said weight having a pair of vertically spaced projections engaging one face of said flange, a clamping element provided with a pad engaging the opposite face of said flange at a point intermediate said pair of vertically spaced projections, said element engaging the face of said weight at a point spaced outwardly from said pad, and adjustable means located intermediate said pad and said point of engagement for securing said weight to said clamping element.

References Cited in the file of this patent UNITED STATES PATENTS 447,607 Gleason Mar. 3, 1891 1,706,407 Miller et a1 Mar. 26, 1929 1,742,552 Manning Jan. 7, 1930 1,770,601 Baker July 15, 1930 1,773,539 Miller Aug. 19, 1930 1,931,472 Archer Oct. 17, 1933 2,123,679 Mahan July 12, 1938 2,270,843 Hartgering et a1 Ian. 27, 1942- 2,441,255 Ashton May 11, 1948 2,575,075 Eaton Nov. 13, 1951 2,605,950 Colvin Aug. 5, 1952 2,618,172 Shoup Nov. 18, 1952 

